1. Field of the Invention
The present invention relates to a blood-vessel endoscope system which is arranged to store a frozen picture in synchronization with heart pulsation.
2. Description of the Related Art
In recent years, endoscopes have been widely used which can be inserted into cavities in living bodies to observe internal organs without any need to substantially cut the living bodies or which can be combined, as required, with medical instruments to observe internal organs in the living bodies.
In general, endoscopes having different constructions are prepared for individual applications.
For example, when the digestive system is to be observed, an endoscope having a relative large diameter is prepared. On the other hand, when the interior of a blood vessel is to be observed, a blood-vessel endoscope having a sufficiently small diameter is used.
As will be described later, during observation or examination using such an endoscope, an endoscopic image is commonly stored/recorded for the purpose of detailed examinations which will be performed later.
If an operator applies the aforesaid blood-vessel endoscope to a portion, such as a coronary artery, which moves vehemently, the operator will encounter the problem that it is difficult to obtain a frozen picture without any large blur by image recording using the blood-vessel endoscope.
An example of a prior art which is close to the present invention is disclosed in Japanese Patent Laid-open No. 80218/1986.
In accordance with the proposal made by the prior art, a gap, which serves as a fluid path, is formed between a tubular member and a cover member for covering and connecting an image guide and a light guide, and the gap or fluid path is connected to a fluid supplying means. The operating timing of a light source for supplying illumination light to the fluid supplying means and the light guide, as well as the operating timing of image memorizing means for recording an optical image transferred through the image guide are placed under electronic control.
After a transparent fluid has been injected from the fluid supplying means into an opaque portion such as a blood vessel, illumination light is transferred from the light source and the image memorizing means is activated. Thus, it is possible to efficiently obtain an observation image even in an opaque liquid.
However, if the arrangement disclosed by the aforesaid prior art is used to obtain a frozen picture of a portion such as a coronary artery whose cardiac muscle moves vehemently, the field of view may be assured but the obtained frozen picture will blur. That is to say, since, in the prior art arrangement, the release timing of a frozen picture is not synchronized with the timing at which the motion of a blood vessel becomes small, the resultant frozen picture will blur. Also, in a blood vessel which shows a vehement motion, the relative position between the blood vessel and the endoscope cannot be fixed. Accordingly, even if a frozen picture of such a blood vessel is imaged, a portion of interest may not be imaged within the frozen picture.
Since the prior art involves the disadvantage described above, it is necessary to carry out imaging again and again in order to obtain the frozen picture required. As a result, a burden imposed on an operator and a patient increases and an additional amount of perfusate must be prepared.
The specification of Japanese Patent Laid-open No. 172621/1984 (or EP Pub. No. 0119614) describes the following arrangement. The leading end of a fiber scope is provided with a fluid sensor for the purpose of measuring the flow rate of an opaque fluid, and a transparent fluid is injected in accordance with the flow rate detected by the sensor so as to obtain an image to be observed.
The arrangement of this prior art is such that the flow rate of transparent fluid is determined by the flow rate of blood. In addition, the specification of the prior art includes a description to the effect that the timing of injecting the transparent fluid is determined by utilizing heart pulsation. However, the description is made with respect to the timing at which the supply of the transparent fluid can be decreased, and the prior art arrangement does not include any means for storing a frozen picture. Accordingly, the aforesaid prior art does not propose or suggest any arrangement which makes it possible to provide a frozen picture without any large blur.